In what circumstances will a jury find that a horse was responsible for the death of a testator?

In Harris v. Mobbs, 3 Ex. D. 268, in an action under Lord Campbell’s Act, by executors, for wrongful and negligent obstruction of the highway, the jury found that the van was left where it stood unreasonably and negligently, and caused some appreciable danger to vehicles passing along the road; that the death of the plaintiffs’ testator was occasioned by the van standing where it did and by the inherent vice of the mare combined; and that there was not contributory negligence; and it was held, on these findings, that the verdict and judgment must be for the plaintiffs; for the unauthorized, unreasonable, and dangerous use of the highway by the defendant was the proximate cause of the injury.